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<title>HLT—Halt </title></head>
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<h1>HLT—Halt</h1>
<table>
<tr>
<th>Opcode</th>
<th>Instruction</th>
<th>Op/En</th>
<th>64-Bit Mode</th>
<th>Compat/Leg Mode</th>
<th>Description</th></tr>
<tr>
<td>F4</td>
<td>HLT</td>
<td>NP</td>
<td>Valid</td>
<td>Valid</td>
<td>Halt</td></tr></table>
<h3>Instruction Operand Encoding</h3>
<table>
<tr>
<td>Op/En</td>
<td>Operand 1</td>
<td>Operand 2</td>
<td>Operand 3</td>
<td>Operand 4</td></tr>
<tr>
<td>NP</td>
<td>NA</td>
<td>NA</td>
<td>NA</td>
<td>NA</td></tr></table>
<h2>Description</h2>
<p>Stops instruction execution and places the processor in a HALT state. An enabled interrupt (including NMI and SMI), a debug exception, the BINIT# signal, the INIT# signal, or the RESET# signal will resume execution. If an interrupt (including NMI) is used to resume execution after a HLT instruction, the saved instruction pointer (CS:EIP) points to the instruction following the HLT instruction.</p>
<p>When a HLT instruction is executed on an Intel 64 or IA-32 processor supporting Intel Hyper-Threading Technology, only the logical processor that executes the instruction is halted. The other logical processors in the physical processor remain active, unless they are each individually halted by executing a HLT instruction.</p>
<p>The HLT instruction is a privileged instruction. When the processor is running in protected or virtual-8086 mode, the privilege level of a program or procedure must be 0 to execute the HLT instruction.</p>
<p>This instruction’s operation is the same in non-64-bit modes and 64-bit mode.</p>
<h2>Operation</h2>
<pre>Enter Halt state;</pre>
<h2>Flags Affected</h2>
<p>None</p>
<h2>Protected Mode Exceptions</h2>
<table class="exception-table">
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<td>#GP(0)</td>
<td>If the current privilege level is not 0.</td></tr>
<tr>
<td>#UD</td>
<td>If the LOCK prefix is used.</td></tr></table>
<h2>Real-Address Mode Exceptions</h2>
<p>None.</p>
<h2>Virtual-8086 Mode Exceptions</h2>
<p>Same exceptions as in protected mode.</p>
<h2>Compatibility Mode Exceptions</h2>
<p>Same exceptions as in protected mode.</p>
<h2>64-Bit Mode Exceptions</h2>
<p>Same exceptions as in protected mode.</p></body></html>